Coded track circuit signaling system



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ZIT AST (CN TKP `l I To Channel 152 0f 51e pping 155| -STE (CN i "emga 1 QTKP See FIGB INVENTOR l s I J Filed April 18, 1942 16 Sheets-Sheet 15 Sept. 5, 1944. N. D. PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEM Filed April 18, 1942 16 Sheets-Sheet 16 @iil E L hwnfor MMM Patented Sept. 5, 1944 CODED TRACK CIR SYS Neil D. Preston, Rochester, N.

General Railway Signal Company,

CUIT SIGNALING TEM Y., assigner to Rochester,

Application April 18, 1942, Serial No. 439,520

80 Claims This invention relates to Signal control systems for railroads, and it more particularly pertains to centralized traflic control systems for single track railroads in which coded track circuits are used for communication of signal controls through the track rails.

In most centralized traffic control systems for stretches of single track remote from a control oflice having passing sidngs associated therewith, signals are located at the ends of the sidings for governing traiiic in both directions. Both the track switches and signals at the ends of the sidings are most generally controlled by an operator at the control oiice, and the switch and signals at each end of each siding constitute a field station. The power operation of the track switches and the clearing of the signals is, however, also dependent upon automatic safety circuits located in the iield and selected in accordance with tralic conditions.

An object of the present invention is to employ coded track circuits, Without the use of line wires, for effecting all desired automatic controls between locations in accordance with traflic conditions, and to communicate manual controls to the switches and signals at the respective eld stations by a line circuit control means such, for example, as by a line circuit code communication system as disclosed in the Judge et al. Patent No. 2,082,544, dated June l, 1937, or by the code communication system disclosed in the Hailes et al. patent, No. 2,259,561, dated Oct. 2l, 1941.

Another object of the present invention is to control the coded track circuits in such a manner as to render them active for the transmission of controls between signal locations only when required for the clearing of signals in accordance 'with the manual control exercised over the communication system from the control cnice. By rendering the track circuit code transmission and reception apparatus normally inactive, there is a substantial saving in energy, and the life of contacts and other moving parts associated with the coded track circuits is substantially prolonged. The saving in energy is of utility particularly where primary batteries are employed.

Another object of the present invention is to govern the initiation and direction of track circuit code transmission in accordance with the direction called for by signal controls communicated from the control oice. The controls are communicated from the control ofce in the usual manner for clearing the respective signais, and the communication of such controls is also effective to initiate the coded track circuit apparatus into operation for the transmission of a driven code through the track rails of the section in advance of the signal to be cleared and in a direction toward such signal from the exit end of the section. This driven code has its rate determined by an oscillator or other impulse forming device which controls the code transmitter for applying such driven code to the track rails at the exit end of the track section. Although the direction of driven code transmission and its initiation are governed by line circuit control from the control oiiice, there are no additional controls required to be communicated from the control oilce to the field stations over what Would be required in the centralized trafc control systems most commonly employed in practice. This is possible because a double use is made of the signal clearing controls communicated from the control office to the field stations.

More specically, the code communication system is so organized that the transmission of a signal clearing code to a selected field station for the head-block signal at one end of a stretch of single track also acts to select the field station at the opposite end of that stretch and effect the energization of a code sending relay at that station. In brief, the two field stations at the opposite ends of each stretch of single track constitute a pair and the transmission of a signal clearing code to either station effects the energization of a code Sending relay at the other. But it should be understood that the usual switch and signal controls can be transmitted to only one station at a time. This is accomplished by employing the usual station selecting apparatus for selecting the stations in pairs and then on a following step of the operating cycle before the controls are transmitted a distinctive impulse (or control) is transmitted to determine which station of the pair is to receive the usual controls and which is to receive the coded track circuit initiation control.

A different mode of operation is employed for each siding track section, that is, the section of main track between the opposite ends of any given siding as distinguished from the siding itself which is usually not track circuited. In this case, the usual signal clearing code is transmitted over the code type communication system to the end of the siding at which an entering signal is to be cleared. The reception of this signal clearing code energizes a signal control relay which not only governs the clearing of the desired signal but also causes a "start irnpulse to be applied across the rails of the siding track section to effect the initiation of the coded track circuit apparatus at the opposite end of such section.

This organization permits the use of the usual station selecting apparatus, as shown for example in the above mentioned patents, without requiring apparatus for decoding every station code at every station, and without requiring additional steps in the cycle of operation of such a system above those usually employed.

Another object of the present invention is to automatically cause the restoration of the coded track circuit apparatus to normal inactive conditions in the rear of a train only if it is not required to be active for the control of signals governing the passage of a following train in the same stretch of track.

Another object of the present invention is to provide coded track circuit signal control means whereby the signals in a stretch of single track between sidings can provide proper indications for the reversal in direction of train operation in such stretch, even if the control of intermediate signals is involved.

Another object of the present invention is to provide means for handling train movements at an outlying switch associated with a stretch of single track extending between passing sidings. It is provided that, after trainmen have been properly instructed by a dispatcher, they can move a train out of an outlying switch under proper signal protection in either direction as manually set up by an operator at the control cnice.

Another object of the present invention, even though the coded track circuit means is normally inactive, is to provide approach and track occupancy indications at the control cnice to correspond with those indications ordinarily provided in the centralized traffic control systems most commonly employed in practice, without the use of line wires except those usually provided for the communication of the indications from the respective iield stations to the control office.

Another object of the invention is to employ inverse codes under certain conditions for approach control, and in connection with the restoration of the track circuit code communication means in the rear of a train, an "inverse code being a code having its impulses transmitted during the "clim periods of a driven code at the opposite end of the track section from the driven code transmitter. Means is provided for checking the inverse code against false operation of the code receiving apparatus by stray currents on the track rails.

Another object of the present invention is to provide adequately for highway crossing signal protection, even though the track circuit code communication means is normally inactive.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, in which corresponding reference characters are used to designate corresponding parts throughout the various figures. in which like letter rei'- erence characters are used to designate devices having similar features and functions. such 1ctter reference characters being generally made distinctive by reason oi preceding numerals indicative of the particular locations or functions with which their devices are associated, and in which:

Fig. l shows diagrammatically the general organization of one embodiment of the present invention, and illustrates the normal conditions of the signals;

Figs. 2A to 2K inclusive show diagrammatically the indications of the signals and the operating conditions of the coded track circuit apparatus under various conditions of traffic;

Fig. 3 illustrates the circuits employed in this embodiment of the present invention at the control ofiice for the selection of various switch and signal control codes for communication over a line circuit extending to the eld stations;

Fig. 4 illustrates the circuits for the stepping relays at the control ofllce, together with the means for transmitting impulses over the line circuit to the field stations, and the control apparatus for receiving indications communicated from the field stations to the control office;

Fig. 5 illustrates, as typical of each of the field stations, the stepping relays and other control apparatus at a particular eld station for the reception of controls from the control oince and for the transmission of indications to the control ofiice by line circuit code;

Fig. 6 illustrates as typical of the respective field stations, the decoding means provided for a pair of field stations for selectively controlling the switch, signal and coded track circuit code sending relays in response to the application of distinctive codes at the control oiflce to the centralized traflic control line circuit extending to the field stations;

Figs. 7A to 7E inclusive, when placed side by side in that order, illustrate in detail the track circuit code communication means for the control of the signals for a particular typical portion of single track chosen for this embodiment of the present invention; and also Fig. 7A may be placed to the right of Fig. 7E for disclosing the circuit organization applying the invention to a siding track section;

Fig. 8 illustrates, as typical of the switch and signal control circuits associated with each end of each of the passing sidings, the switch and signal control circuits for a particular end of a certain one of the passing sidngs;

Fig. 9 illustrates how the system provided by the present invention can be adapted to a condition in which highway crossing signals are involved;

Fig. 10 illustrates a means for checking the operation of a series track circuit relay;

Fig. 11 illustrates a means for governing the energization of an indicator lamp for a siding track section in accordance with the indications communicated to the control oiiice from the field stations at the ends of such siding track section.

Fig. 12 illustrates a modified form of the invention in which manual control of an entering signal for a siding can impress driven code in the rear of such signal for "back-up train movements as well as other conditions shown in Figs. "7A to 7C.

Fig. 13 illustrates a modled arrangement suitable for two pairs of intermediate signals,

For the purpose oi simplifying the illustration of this embodiment of the present invention and facilitating in the explanation thereof, various parts and circuits have been shown diagrammatically rather than showing the specific construction and arrangement of parts that would be employed in practice. The various relays and their contacts are illustrated in a conventional manner and symbols are used to indicate connections to the terminals of batteries or other sources of electric current instead of showing all of the wiring connections to the terminals. For convenience in simplifying the drawings, certain of the relay contacts have been shown in a conventional written circuit manner, such contacts being identified as associated with particular relays because of the reference characters of such relays respectively appearing above those contacts.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of direct current, and the circuits with which those symbols are used always have current flowing in the same direction. If alternating current is to be used, the symbols (-1-) and are to be considered as instantaneous relative polarities.

In describing the present invention, reference is made from time to time to functions common to all parts of a similar character by use of the letter reference characters common to such parts without the preceding numerals characteristic of the locations or devices with which the respective parts are associated.

Track layout-With reference to Fig. l, the typical stretch of track chosen for this embodiment of the present invention is illustrated as a main stretch of single track having passing sidings A and B associated therewith. The siding A is connected to the main stretch of track by the track switch 2W at the right-hand or east end of the passing siding, and the passing siding B is connected to the main stretch of track by the track switches 3W and 4W for the respective west and east ends of the siding. It will be readily apparent, as the description oi the present invention progresses, that the control apparatus and circuits provided for the particular track layout illustrated in Fig. 1 are of such a nature that they can be readily modified by those skilled in the art to render them applicable to various other track layouts requiring a different location of the signals, a different spacing of the passing sidings, or a greater number of track sections in the stretches of single track between sidings.

The track switch at each end of the sidings is power operated in this embodiment of the present invention, but it will be readily apparent to those skilled in the art how the system can be modified to be adapted to systems in which the track switches are hand operated. The track switch 3W, for example, is power operated by a switch machine 3SM (see Fig. 8) which can be, for example, of the character disclosed in the patent to W. K. Howe, Patent No. 1,466,903, dated September 4, 1923. Suitable remote switch control apparatus such as shown, for example, in the patent to Hoppe et al., Patent No. 1,877,876, dated Sept. 20, 1932, is preferably employed to provide features such as overload protection and the like. For a proper protection of the track switch 3W against unsafe operation, a short detector track section 6--1T is provided for the track switch, such detector track section having the usual type of steadily energized track circuit with the track switch properly bonded to provide fouling protection.

In this disclosure the signals at the ends of the fill fill

sidings governing tramo away from the siding are called leaving signals or head block signels," while the signals governing entrance to the siding or to the main track associated therewith are called entering signals. For example, signais 2 and 2A are head block signals at siding A for governing eastbound traiiic; while signals 1 and 1A are at siding B for governing westbound traffic. Signals 3 and 3A are entering signals for governing westbound traflic entering the siding section or the siding A respectively; while signals 6 and BA are for governing eastbound traffic over the siding section or on to the siding'B respectively. Similar signals are entering signals usually provided for governing the traflic at the ends of the various sidings of any single track railroad.

Between the sidings A and B, only a double intermediate signal location, having signals 4 and 5 for governing eastbound and westbound trafllc respectively, has been shown, but it should be understood that any number of double intermediate signal locations may be provided in practice, or single intermediate locations may be placed at so-called staggered locations.

The signal symbols employed in the track diagrams of this embodiment of the present invention are to be considered as indicative of the signal aspects under various conditions of traffic, rather than being indicative of a particular type of signal employed, as it will be readily understood by those familiar with the art that any suitable type of a signal can be employed with the system provided by the present invention. Thus, although semaphore signals, position light signals or light signals having individual color lamp units can be employed, the signals used in this embodiment of the present invention are of the searchlight type such as disclosed, for example, in the patent to O. S. Field, Patent No. 1,835,150, dated December 8, 1931. Each of the searchlight signals when deenergized, displays a red indication for danger or stop, and when energized with a particular polarity provides a yellow indication for caution, and when energized with the opposite polarity provides a green indication for clear. The display of the indications of certain of the signals becomes effective only upon the approach of a train.

A neutral polar relay WP (see Fig. 8) is associated with each of the track switches in the usual manner for repeating the correspondence condition of the switch points with the switch machine mechanism. Each of the WP relays is normally energized with a polarity selected in accordance with the normal or reverse position of the track switch with which it is associated. When the switch machine mechanism and/ or the switch points becomes unlocked from either the normal position or the reverse position, the relay WP associated therewith is dropped away.

The trackway is divided into track sections in the usual manner, the siding section 3T being associated with the siding A, the track sections 2-5T and 4-1T being included in the stretch of single track between the sidings A and B, and the siding section 6-9T being associated with the passing siding B. Each of such track sections have coded track circuits including code transmitters and receivers at their opposite ends, while the detector track sections 2-3T, B-'IT and B--BT are steadily energized.

For convenience in considering certain attributes of the present invention, the embodi ment of the present invention indicates how the main stretch of single track can have associated therewith an outlying switch (see Fig. 7D). This outlying switch W is assumed to be hand operated by a trainman in accordance with instructions from the dispatcher.

With reference to Fig. 9, it is illustrated how highway crossing signals can be governed if there is a highway crossing to be protected in the stretch of single track between two passing sidings. Itis believed that it will be readily apparent as the description progresses how the principles of control for the highway crossing signals can readily be applied to provide highway crossing protection where a highway crosses at a siding.

Communication system devices-To simplify the disclosure of the present invention reference is to be made to the patent to Judge et al., Patent No. 2,082,544, dated June l, 1937, for a detailed description of the line circuit communication system employed for the communication of switch and signal controls from the control office to the respective field stations. In order that the description of such Judge et al. patent can be readily applied to the communication system of this embodiment of the present invention, the letter reference characters for the various devices of the communication system in the drawings of this disclosure are similar to the reference characters for corresponding parts disclosed in the Judge et al. patent.

The control office communication apparatus comprises change relays CH (see Fig. 3) used for initiating the system into operation responsive to the manual actuation of their respective start buttons SB for causing the transmission of the desired controls as selected by the actuation of switch and signal control levers SML and SGL respectively. The relays CD, CDS, CHP and C are provided to maintain a particular order in the transmission of controls during successive control cycles of operation when controls for more L than one field station are ready to be transmitted at the same time. The selective energization of the relays NC and PC at the control office in accordance with the code selected by the code determining relays CD, applies impulses of selected polarities to the line circuit for transmission to the field stations. The relays E and EP (see Fig. 4) provide the pulsing of the line circuit while the line relay F follows the pulsing, and its repeater relays FP and ZFP operate the control oflice stepper consisting of stepping relays IV, 2V, 3V, 4V, 5V, LV and the half-step relay VP. The slow release relays SA and 2SA (see Fig. 4) are used as cycle marking relays, and the relays MF, MB, DV and FC are used in connection with the reception of indications communicated from the respective field stations.

The field station communication apparatus for each of the field stations is similar to that illustrated in Fig. 5 for a particular one of the field stations. Such apparatus comprises a line relay F, a line repeater relay FP, cycle marking relays SA and SB, station selecting relays SO and SOS, decoding relays PS and NS, a field station stepper consisting of stepping relays IV, 2V, 3V, 4V, 5V and LV, a half step relay VP, and relays PF, PB, LO and CH which are associated with the transmission of indications.

Each of the field locations is provided with relays which are manually controlled from the control oice for governing the switch and signais and initiating the coded track circuit apparatus into operation. For example, the eld station number 2A is provided with switch control relays 2WN and 2WR, as well as signal CP for that end of the control relays 2LD and ZRD which are employed for controlling the clearing of the signals for the left or right hand direction at that station. The relay 2B is remotely controlled for restoring the signals at that location to stop conditions. When a code is received which should cause the initiation of the coded track circuit apparatus, the relay 2CS is picked up as will be described in detail hereinafter. Similar apparatus is, of course, provided for the eld station number 2B.

Track circuit and signal control devices.-Each of the coded track circuits has a code transmitter relay CP (see Figs. 7A to '7E inclusive), and a code receiving track relay TR associated with each end thereof. It is preferable that each o1' the track relays TR have a polar structure arranged in such a manner as to cause the picking up of the armature of the relay only if that relay is energized with a particular polarity although such characteristics are not essential for practising the invention. Such a type of polar track relay is desirable for providing broken down joint protection.

A neutral code following repeater relay TP is provided for each of the relays TR, and such TP relay provides for the energization of a decoding transformer TF, the secondary winding of which provides for the energization of a relay H that is picked up when a seventy-live code or a code of any higher rate is being received. A secondary winding of certain of the transformers TF provides for the energization of a tuned circuit for the control of a relay D which is responsive only to the reception of a particular code such as a code of rate.

The code transmitter relay CP for the end of each of the track sections at each of the field stations has associated therewith a code sending relay CS which is effective when energized to cause the transmission of a driven code by the relay CP for that end of the track section. Under certain conditions when the track circuit code communication system is active, the relay CS is effective when deenergized to render the relay track section active for the transmission of an inverse code.

The coders or oscillators i200 and 15C are impulse forming devices, and the relay CP for each end of each of the coded track circuits repeats the impulses produced by one or the other of such coders at that location when it transmits driven code pulses over the track rails. The coders |2UC and 15C are preferably of the oscillatory type having a magnetically rotated balance wheel acting in opposition to a clock spring to provide an oscillating operation. By using balance wheels of different weights, the different desired codes are produced. It is to be understood, however, that various types of impulse producing devices place of the oscillators i200 and 15C of this embodiment of the present invention and different rates of impulse transmission can be employed. Although similar oscillators for the various locations have been illustrated as having the same reference characters, it is to be undertion system is to be set into operation.

The proceed and danger indications of the various searchlight signals are repeated by respective YGP and RGP relays as typically illustrated 

